字符计数忽略多个字符串中的第一个字符

Question

#include <iostream>
using namespace std;

int main()
{
    string sentence;
    int countv = 0, countc = 0, countspace = 0, number, s = 1;
    cout << "How many sentence would you like to check? - ";
    cin >> number;
    
    while(s <= number)
    {
        cout << "\nSentence " << s << ":";
        cin.ignore();
        getline(cin, sentence);
        
        for(int i = 0; i < sentence.length(); i++)
        {
            if(sentence[i] == 'a' || sentence[i] == 'e' || sentence[i] == 'i' || sentence[i] == 'o' || sentence[i] == 'u')
                countv++;
            else if(isspace(sentence[i]))
                countspace++;
            else
                countc++;
        }
        cout << "\nSentence " << s << " result:";
        cout << "\nThere are " << countv << " vowels in the sentence.";
        cout << "\nThere are " << countc << " consonants in the sentence.";
        cout << "\nThere are " << countspace << " whitespace in the sentence.";
        countc = 0, countv = 0, countspace = 0;
        s++;
        cout << "\n";
    }
}

我正在尝试计算多个字符串中元音和辅音的数量，但出于某种原因，它只为第一个字符串提供正确的 output。

我注意到，对于下一个字符串（第二个、第三个等等），它不计算字符串的第一个字母。 为什么是这样？

Answer 1

该代码忽略了第一个字符串之后的每个字符串的第一个字符，因为您告诉它忽略输入中的那些字符……通过调用cin.ignore() 。 该调用不应在循环内，而应紧接在循环之前，以便忽略cin >> number提取后留在输入 stream 中的换行符。

请注意，对getline的调用不会将该换行符留在流的缓冲区中； 请参阅 此 cppreference 页面：

…下一个可用的输入字符是delim ，正如Traits::eq(c, delim)测试的那样，在这种情况下，分隔符是从 input 中提取的，但没有附加到str 。

这是您的代码的适当修改版本：

#include <string>
#include <iostream>
using std::cin, std::cout;

int main()
{
    std::string sentence;
    int countv = 0, countc = 0, countspace = 0, number, s = 1;
    cout << "How many sentence would you like to check? - ";
    cin >> number;
    cin.ignore(); // Call ignore HERE (once) to skip the newline left in the buffer from the above!

    while (s <= number)
    {
        cout << "\nSentence " << s << ":";
     //  cin.ignore(); WRONG!
        std::getline(cin, sentence);

        for (size_t i = 0; i < sentence.length(); i++)
        {
            if (sentence[i] == 'a' || sentence[i] == 'e' || sentence[i] == 'i' || sentence[i] == 'o' || sentence[i] == 'u')
                countv++;
            else if (isspace(sentence[i]))
                countspace++;
            else
                countc++;
        }
        cout << "\nSentence " << s << " result:";
        cout << "\nThere are " << countv << " vowels in the sentence.";
        cout << "\nThere are " << countc << " consonants in the sentence.";
        cout << "\nThere are " << countspace << " whitespace in the sentence.";
        countc = countv = countspace = 0; // Nicer than the dodgy use of the comma!
        s++;
        cout << "\n";
    }
}